Modern rifle bullets must sufficiently meet the various requirements of hunting. The most important of these requirements is target accuracy, that is, bullets must ensure shooting precision from various hunting firearms. Furthermore, the target should be killed with as little suffering as possible. For these reasons a good cross-sectional expansion and penetration of the bullet in the target is necessary. To fulfill these requirements, the bullet must simultaneously increase in cross section and lose as little weight as possible to fragmentation upon entering the target. An additional requirement for modern rifle bullets is that they cause clearing of hair and bleeding at the entry wound to make any potential pursuit easier even in the absence of an exit wound.
Because the entry wound frequently closes very quickly due to the elasticity of the coat, the hide, and the underlying layer of fat, an exit wound with bleeding is desirable even when a shot is made at an unfavorable angle.
These requirements posed by hunting are well satisfied by the rifle bullets developed by Brenneke GmbH (D-30851 Langenhagen, Germany) and known worldwide under the brand names TUG™ (Torpedo-Universal-Bullet) and TIG™ (Torpedo-Ideal-Bullet). These bullets constitute jacketed hollow point bullets with nickel-plated mild steel jackets which are formfitting around dual lead cores consisting of a forward, soft lead core and of an aft, hard lead core. The brand names denote the torpedo-shaped bases found in these bullets.
This base form has certain advantages in terms of interior ballistics. The dual core construction of the Brenneke rifle bullets mentioned above facilitates an optimal energy transfer in the target with reliable expansion and penetration. This results in the very rapid deformation of the soft, forward lead core, which is slowed by the harder, aft lead core and the gradually increasing thickness of both the bullet jacket and of the necking region in the tail. Upon entering the target, these bullets may partially fragment.
However, the hard, aft lead core results in the desired exit wound in most cases.
Characteristic of the TIG and TUG-bullets is a sharp edge formed behind the bullet tip, which in most cases causes cut hair and bleeding at the entry wound.
Another jacketed hollow point bullet with a dual core is described in EP 0 225 532 A1. The aft core is made of lead and is partly surrounded by an inner jacket. The aft core is held together with the inner jacket through the radial impression of the outer jacket on the inner jacket. The aft core is made of lead, while the forward core can be made of lead or a lead-free material such as zinc, tin, or copper to prevent lead-contamination of the target. No claims are made regarding the material of the outer jacket. The bond between the cores and both the inner and outer jackets is provided through a form fit. Furthermore, the bullet is characterized by a hollow point, which functions to accelerate the mushrooming.
When hitting the target, the tip first exhibits outward radial expansion before rearward folding. The forward region of the aft lead core is thereby strongly compressed, whereby the core together with the inner jacket exhibits strong outward radial expansion. A mechanical bond thereby occurs involving the aft core, the inner jacket, and the outer jacket.
The aft core therefore remains tightly bonded to the mushroomed outer jacket. When the outer jacket mushrooms, the radial indentation forms a barrier against further mushrooming due to its increased resistance moment.
Because that rifle bullet does not have a sharp edge, it ensures neither clearing of hair nor bleeding at the entry wound. Furthermore, that bullet partly fragments in the target simply upon displacement of the forward core. As a result, that bullet loses mass and an exit wound, at least in cases of unfavorable angle of shot, is not ensured.
In DE 38 40 165 A1 a lead-free rifle bullet is described that is also a jacketed hollow point bullet. The jacket is made of red brass or mild steel. It can be closed at the aft region, that is, at the base, or it can rest as a nipple on the bullet core. The bond between jacket and bullet core is formed through material bonding, e.g. through soldering or through the introduction of a channel in the outer jacket, which is pressed into the bullet core. The forward edge of the jacket extends radially outwardly of the bullet core, and can be configured as a sharp edge.